Range compensators for radiation therapy

ABSTRACT

A system for treating a patient during radiation therapy includes range compensators. Each of the range compensators shapes a distribution of a dose delivered to the patient by a beam emitted from a nozzle of a radiation treatment system. A positioning component holds the range compensator in place relative to the patient such that the range compensator lies on a path of the beam.

BACKGROUND

The use of radiation therapy to treat cancer is well known. Typically,radiation therapy involves directing a high energy beam of radiationinto a target (e.g., a tumor or lesion) in a patient.

A radiation therapy device typically includes, among other components, aplatform (e.g., a table or couch) to support the patient and a nozzlethat emits the radiation beam. The patient is in a supine position, forexample, and the nozzle directs the beam into the target (e.g., thetumor being treated).

During treatment, it is important to keep the patient as stationary(immobilized) as possible, so that the beam remains pointed at thetarget and at the proper place within the target. Otherwise, theradiation beam may miss parts of the target or might land on normal(healthy) tissue outside the target. Fixation or immobilization devicesare used to secure a patient's position and keep the patient stationaryduring radiotherapy.

A standard treatment process includes scanning and imaging the patientprior to treatment to detect internal organs and locate the target(e.g., the tumor). Immobilization devices customized for the patient aredesigned and a treatment plan is generated. The designs for theimmobilization devices are sent to a manufacturer. The manufacturedimmobilization devices are delivered to the treatment center, where theyare tested prior to beginning radiotherapy. If changes are needed, thenthe process of interacting with the manufacturer is repeated. Thepatient then returns and treatment can begin.

The conventional approach described above is problematic for a varietyof reasons. First, multiple patient visits are required—at least onevisit is required prior to treatment in order to design theimmobilization devices. Also, the need to involve a manufacturerincreases costs. Furthermore, time may be lost while the immobilizationdevices are shipped from and perhaps back to the manufacturer.

Also during treatment, the nozzle and/or the patient are typically movedrelative to one another so that the beam can be directed into the targetfrom different directions/angles (beam geometries). The target may havean irregular shape and/or the amount (depth) of normal, healthy tissueon the beam path may vary depending on the beam geometry. In general, itmay be necessary to shape the dose distribution delivered by a beamaccording to the shape and depth of the target and the beam geometry.

A range compensator is used to change (e.g., decrease) the energies ofparticles in a beam to affect the distance that the beam penetrate intothe target. The range compensator may be located downstream of theparticle accelerator before the nozzle or in the nozzle itself.

A recent radiobiology study has demonstrated the effectiveness ofdelivering an entire, relatively high therapeutic radiation dose to atarget within a single, short period of time. This type of treatment isreferred to generally herein as FLASH radiation therapy (FLASH RT).Evidence to date suggests that FLASH RT advantageously spares normal,healthy tissue from damage when that tissue is exposed to only a singleirradiation for only a very short period of time. In general, because ofthe higher dose rates associated with FLASH RT, it is desirable tominimize the amount of time that normal, healthy tissue outside thetarget is irradiated. A means of achieving that is to produce aradiation treatment plan in which beams do not overlap, or overlap aslittle as possible, outside the target. With FLASH RT, thedirection/angle of the nozzle is set so that the nozzle is aimed at thetarget; the range compensator is adjusted to account for the beamenergy, the distance to the target, and the shape of the target (thedistance across the target); and then the beam is turned on and quicklyturned off. The process is repeated for the next beam geometry. Toreduce overall treatment time for the comfort of the patient, it isdesirable to be able quickly adjust the range compensator for thedifferent beam geometries.

SUMMARY

In embodiments, an immobilization device for limiting movement of apatient on a patient support device during radiation therapy includes arange compensator and a positioning component. The range compensatorshapes a distribution of a dose delivered to a patient by an incidentbeam emitted from a nozzle of a radiation treatment system. The dosedistribution may be relatively uniform across the target, or it may benon-uniform (e.g., the distribution may include a Bragg peak). Thepositioning component holds the immobilization device in place relativeto the patient. In effect, in one or more such embodiments, the rangecompensator is moved from the nozzle of a radiation treatment system tothe immobilization device. This multi-functional aspect of theimmobilization device can improve radiation treatments and reduce costs.

The immobilization device can be fabricated using a three-dimensionalprinter. Accordingly, patient-specific devices can be readily, quickly,inexpensively, and effectively produced on-site without an externalmanufacturer, avoiding shipping from and perhaps back to themanufacturer. The number of patient visits can be reduced because, forexample, the immobilization device can be fabricated when the patientarrives for a treatment and/or because the immobilization device can bequickly modified on-site after testing for fit and/or function or whilethe radiation therapy is being performed. Furthermore, theimmobilization devices can be recycled and do not need to be stored,which contributes to the cost savings.

In embodiments, a system for treating a patient during radiation therapyincludes multiple range compensators. In practice, each rangecompensator is located on the patient. At least one positioningcomponent holds the range compensators in place relative to the patientsuch that each range compensator lies on a path of a beam emitted from anozzle of a radiation treatment system. In embodiments, at least one ofthe range compensators is part of an immobilization device such as theaforementioned immobilization device. Each of the range compensatorsshapes a distribution of a dose delivered to the patient by the beam.The dose distribution may be relatively uniform across the target, or itmay be non-uniform (e.g., the distribution may include a Bragg peak). Ineffect, in embodiments, the range compensator is moved from the beamdelivery system (e.g., from the nozzle) of a radiation treatment systemto a location on the patient.

In another embodiment, a computer-implemented method of radiationtreatment planning includes accessing, from a memory of the computer,parameters for a radiation treatment plan. The parameters include, forexample, the number of beams and paths of the beams relative to aposition of a patient on a patient support device. Locations on thepatient for range compensators are identified. Specifically, each rangecompensator is located on the patient so that each range compensatorlies on at least one of the beam paths.

In another embodiment, a computer-implemented radiation treatment methodincludes accessing, from a memory of the computer, a radiation treatmentplan that prescribes a distribution of a dose to be delivered to atarget in a patient by a number of beams emitted from a nozzle of aradiation treatment system. The nozzle is controlled to aim the beams atrange compensators positioned at different locations on the patient. Thenozzle is aimed at a first range compensator, and then a first beam isturned on and emitted at the first range compensator. The first beam isthen turned off, the nozzle is aimed at a second range compensator, anda second beam is turned on and emitted at the second range compensator.This process can be repeated for each of the number of beams.

Range compensators in embodiments according to the invention can be usedto shape dose distribution in the target in lieu of, but also incombination with, a conventional range compensator. By strategicallylocating the range compensators on the patient, different beamgeometries are readily accommodated. It is not necessary to wait until arange compensator is adjusted when the beam geometry changes; instead, aproperly configured range compensator is already in place. Thus,radiation therapy can be quickly performed, thereby facilitating patientcomfort. Range compensators in embodiments according to the inventionalso can be used to provide the prescribed dose inside the target andthus can facilitate radiation treatment planning using FLASH RT bymaking it easier to address that aspect of the planning.

These and other objects and advantages of embodiments according to thepresent invention will be recognized by one skilled in the art afterhaving read the following detailed description, which are illustrated inthe various drawing figures.

This summary is provided to introduce a selection of concepts in asimplified form that is further described below in the detaileddescription that follows. This summary is not intended to identify keyfeatures or essential features of the claimed subject matter, nor is itintended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification and in which like numerals depict like elements,illustrate embodiments of the present disclosure and, together with thedetailed description, serve to explain the principles of the disclosure.

FIG. 1 shows a block diagram of an example of a computing system uponwhich the embodiments described herein may be implemented.

FIG. 2 is a block diagram showing selected components of a radiationtreatment system upon which embodiments according to the presentinvention can be implemented.

FIG. 3 illustrates elements of a radiation treatment system inembodiments according to the invention.

FIG. 4 is a block diagram illustrating components in a process forcreating immobilization devices in embodiments according to the presentinvention.

FIGS. 5A, 5B, 5C, and 5D illustrate immobilization devices inembodiments according to the present invention.

FIG. 6 is a flowchart of an example of computer-implemented operationsfor producing an immobilization device in embodiments according to thepresent invention.

FIG. 7 is a flowchart of an example of computer-implemented operationsfor performing radiation treatment in embodiments according to thepresent invention.

FIG. 8A is a system for treating a patient during radiation therapy inembodiments according to the present invention.

FIG. 8B illustrates a perspective view of an example of a beam geometryin embodiments according to the invention.

FIG. 8C illustrates a perspective view of an example of a beam geometryin embodiments according to the invention.

FIG. 9 is a flowchart of an example of computer-implemented operationsfor radiation treatment planning in embodiments according to the presentinvention.

FIG. 10 is a flowchart of an example of computer-implemented operationsfor radiation treatment in embodiments according to the presentinvention.

DETAILED DESCRIPTION

Reference will now be made in detail to the various embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. While described in conjunction with theseembodiments, it will be understood that they are not intended to limitthe disclosure to these embodiments. On the contrary, the disclosure isintended to cover alternatives, modifications and equivalents, which maybe included within the spirit and scope of the disclosure as defined bythe appended claims. Furthermore, in the following detailed descriptionof the present disclosure, numerous specific details are set forth inorder to provide a thorough understanding of the present disclosure.However, it will be understood that the present disclosure may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail so as not to unnecessarily obscure aspects of the presentdisclosure.

Some portions of the detailed descriptions that follow are presented interms of procedures, logic blocks, processing, and other symbolicrepresentations of operations on data bits within a computer memory.These descriptions and representations are the means used by thoseskilled in the data processing arts to most effectively convey thesubstance of their work to others skilled in the art. In the presentapplication, a procedure, logic block, process, or the like, isconceived to be a self-consistent sequence of steps or instructionsleading to a desired result. The steps are those utilizing physicalmanipulations of physical quantities. Usually, although not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated in a computing system. It has proven convenient at times,principally for reasons of common usage, to refer to these signals astransactions, bits, values, elements, symbols, characters, samples,pixels, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present disclosure,discussions utilizing terms such as “accessing,” “controlling,”“identifying,” “aiming,” “turning on,” “turning off,” or the like, referto actions and processes (e.g., the flowcharts of FIGS. 6, 7, 9, and 10) of a computing system or similar electronic computing device orprocessor (e.g., the computing system 100 of FIG. 1 ). The computingsystem or similar electronic computing device manipulates and transformsdata represented as physical (electronic) quantities within thecomputing system memories, registers or other such information storage,transmission or display devices. Terms such as “dose” or “energy”generally refer to a dose or energy value; the use of such terms will beclear from the context of the surrounding discussion.

Portions of the detailed description that follows are presented anddiscussed in terms of a method. Although steps and sequencing thereofare disclosed in figures herein (e.g., FIGS. 6, 7, 9, and 10 )describing the operations of this method, such steps and sequencing areexemplary. Embodiments are well suited to performing various other stepsor variations of the steps recited in the flowchart of the figureherein, and in a sequence other than that depicted and described herein.

Embodiments described herein may be discussed in the general context ofcomputer-executable instructions residing on some form ofcomputer-readable storage medium, such as program modules, executed byone or more computers or other devices. By way of example, and notlimitation, computer-readable storage media may comprise non-transitorycomputer storage media and communication media. Generally, programmodules include routines, programs, objects, components, datastructures, etc., that perform particular tasks or implement particularabstract data types. The functionality of the program modules may becombined or distributed as desired in various embodiments.

Computer storage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules or other data. Computer storage media includes, but isnot limited to, random access memory (RAM), read only memory (ROM),electrically erasable programmable ROM (EEPROM), flash memory or othermemory technology, compact disk ROM (CD-ROM), digital versatile disks(DVDs) or other optical storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium that can be used to store the desired information and that canaccessed to retrieve that information.

Communication media can embody computer-executable instructions, datastructures, and program modules, and includes any information deliverymedia. By way of example, and not limitation, communication mediaincludes wired media such as a wired network or direct-wired connection,and wireless media such as acoustic, radio frequency (RF), infrared andother wireless media. Combinations of any of the above can also beincluded within the scope of computer-readable media.

FIG. 1 shows a block diagram of an example of a computing system 100upon which the embodiments described herein may be implemented. In itsmost basic configuration, the system 100 includes at least oneprocessing unit 102 and memory 104. This most basic configuration isillustrated in FIG. 1 by dashed line 106. The system 100 may also haveadditional features and/or functionality. For example, the system 100may also include additional storage (removable and/or non-removable)including, but not limited to, magnetic or optical disks or tape. Suchadditional storage is illustrated in FIG. 1 by removable storage 108 andnon-removable storage 120. The system 100 may also containcommunications connection(s) 122 that allow the device to communicatewith other devices, e.g., in a networked environment using logicalconnections to one or more remote computers.

The system 100 also includes input device(s) 124 such as keyboard,mouse, pen, voice input device, touch input device, etc. Outputdevice(s) 126 such as a display device, speakers, printer, etc., arealso included.

In the example of FIG. 1 , the memory 104 includes computer-readableinstructions, data structures, program modules, and the like. Dependingon how it is to be used, the system 100—by executing the appropriateinstructions or the like—can be used to implement a planning system usedto create immobilization devices using a three-dimensional (3D) printer,as a control system to implement a radiation treatment plan in aradiation treatment system, or to implement a system for radiationtreatment planning.

FIG. 2 is a block diagram showing selected components of a radiationtreatment system 200 upon which embodiments according to the presentinvention can be implemented. In the example of FIG. 2 , the system 200includes an accelerator and beam transport system 204 that generatesand/or accelerates a beam 201. Embodiments according to the inventioncan generate and deliver proton beams, electron beams, neutron beams,photon beams, ion beams, or atomic nuclei beams (e.g., using elementssuch as carbon, helium, or lithium). The operations and parameters ofthe accelerator and beam transport system 204 are controlled so that theintensity, energy, size, and/or shape of the beam are dynamicallymodulated or controlled during treatment of a patient according to aradiation treatment plan.

A recent radiobiology study has demonstrated the effectiveness ofdelivering an entire, relatively high therapeutic radiation dose to atarget within a single, short period of time. This type of treatment isreferred to generally herein as FLASH radiation therapy (FLASH RT).Evidence to date suggests that FLASH RT advantageously spares normal,healthy tissue from damage when that tissue is exposed to only a singleirradiation for only a very short period of time. For FLASH RT, theaccelerator and beam transport system 204 can generate beams that candeliver at least four (4) grays (Gy) in less than one second, and maydeliver as much as 20 Gy or 50 Gy or more in less than one second.

The nozzle 206 is used to aim the beam toward various locations (atarget) within a patient supported on the patient support device 208(e.g., a chair, couch, or table) in a treatment room. A target may be anorgan, a portion of an organ (e.g., a volume or region within theorgan), a tumor, diseased tissue, or a patient outline.

The nozzle 206 may be mounted on or may be a part of a gantry (FIG. 3 )that can be moved relative to the patient support device 208, which mayalso be moveable. In embodiments, the accelerator and beam transportsystem 204 is also mounted on or is a part of the gantry; in anotherembodiment, the accelerator and beam transport system is separate from(but in communication with) the gantry.

The control system 210 of FIG. 2 receives and implements a prescribedtreatment plan. In embodiments, the control system 210 includes acomputing system having a processor, memory, an input device (e.g., akeyboard), and perhaps a display; the system 100 of FIG. 1 is an exampleof a platform for the control system 210. The control system 210 canreceive data regarding operation of the system 200. The control system210 can control parameters of the accelerator and beam transport system204, nozzle 206, and patient support device 208, including parameterssuch as the energy, intensity, size, and/or shape of the beam, directionof the nozzle, and position of the patient support device (and thepatient) relative to the nozzle, according to data the control system210 receives and according to the radiation treatment plan.

Immobilization Device Including Range Compensator for Radiation Therapy

FIG. 3 illustrates elements of a radiation treatment system 300 fortreating a patient 304 in embodiments according to the invention. Thesystem 300 is an example of an implementation of the radiation treatmentsystem 200 of FIG. 2 , for example. In embodiments, the gantry 302 andnozzle 306 can be moved up and down the length of the patient 304 and/oraround the patient, and the gantry and nozzle can move independently ofone another. In embodiments, the patient support device 308 can be movedto different positions relative to the gantry 302 and nozzle 306,rotated about its longitudinal axis, rotated about a central (normal)axis, and/or tilted back and forth about a transverse axis. While thepatient 304 is supine in the example of FIG. 3 , the invention is not solimited. For example, the patient 304 can instead be seated in a chair.

In embodiments according to the invention, an immobilization device 320is placed next to and against the patient 304 on the patient supportdevice 308 during radiation therapy. The placement of the immobilizationdevice 320 and the shape and relative size of the device shown in theexample of FIG. 3 are examples only. In embodiments, the immobilizationdevice 320 is worn by the patient 304. The immobilization device 320 canbe custom-designed to fit the contours of the body of the patient 304.In general, the immobilization device 320 is a patient-specific device.That is, the immobilization device 320 is designed for and used by asingle patient.

The immobilization device 320 helps to establish a fixed, definedlocation for the patient 304 on the patient support device 308 and alsohelps to establish a position (e.g., posture) for the patient. Animmobilization device also helps to maintain the patient in theestablished location and position during the course of a radiationtreatment session and to re-establish and maintain the patient'slocation and position in subsequent treatment sessions. In embodimentsaccording to the invention, the immobilization device 320 has a shapethat provides these functionalities. Such shapes are known in the art.

Conventionally, an immobilization device is placed so that it does notobstruct the path of the beam. In contrast, in embodiments according tothe invention, the immobilization device 320 is placed in the beam path,between the nozzle 306 and a target in the patient 304, so that the beampasses through the immobilization device on its way to the target.

Thus, in embodiments, another purpose of the immobilization device 320is to ensure that any path of a radiation beam from the nozzle 306 to atarget inside the patient 304 will travel through substantially the sameeffective thickness of matter. That is, depending on the shape of thepatient's body, the location of the target in the patient, and the shapeof the target, a beam may pass through different amounts (depths) oftissue if those variables are not compensated for. Similarly, two ormore beams that have parallel paths may each pass through differentamounts of tissue. The shape of the immobilization device 320 can bedesigned to compensate for these types of differences. Thus, for beamssuch as proton beams, electron beams, neutron beams, photon beams, ionbeams, and atomic nuclei beams, a uniform (or nearly uniform) dose canbe delivered across the length (depth) of the target using a beam orbeams that pass through the immobilization device 320.

Also, for proton beams and ion beams, the immobilization device 320 canbe designed to locate the Bragg peak of the beam inside the target.Specifically, the Bragg peak can be located at the distal portion oredge of the target, and then moved along the beam path toward theproximal edge of the target by changing the beam energy to achieve aSpread Out Bragg Peak (SOBP). Also, as will be described (see FIG. 5A),the shape of the immobilization device 320 can be designed to achieve anSOBP.

The immobilization device 320 of FIG. 3 can be advantageously utilizedwith FLASH RT, although the invention is not so limited. In general,because of the higher dose rates associated with FLASH RT as mentionedabove, it is desirable to minimize the amount of time that normal,healthy tissue outside the target is irradiated. A means of achievingthat is to produce a radiation treatment plan in which beams do notoverlap, or overlap as little as possible, outside the target. Anothermeans of achieving that is to specify, during radiation treatmentplanning, limits for a maximum irradiation time and a minimum dose ratefor normal, healthy tissue outside the target. However, it is stillnecessary to deliver the prescribed dose into and uniformly across thetarget. Immobilization devices in embodiments according to the inventioncan provide a uniform dose into and across a target and thus canfacilitate radiation treatment planning using FLASH RT by resolving orcontributing to the resolution of that aspect of the planning.

As mentioned above, immobilization devices can be created by 3D-printingusing a 3D printer. FIG. 4 is a block diagram illustrating components ina process 400 for creating immobilization devices in embodimentsaccording to the present invention.

In the example of FIG. 4 , a patient (e.g., the patient 304) is imagedusing an image system 402 that uses, for example, x-rays, magneticresonance imaging (MRI), and computed tomography (CT). When CT or MRIimagery, for example, is used, a series of two-dimensional (2D) imagesare taken from a 3D volume. Each 2D image is an image of across-sectional “slice” of the 3D volume. The resulting collection of 2Dcross-sectional slices can be combined to create a 3D model orreconstruction of the patient's anatomy (e.g., internal organs). The 3Dmodel will contain organs of interest, which may be referred to asstructures of interest. Those organs of interest include the organtargeted for radiation therapy (a target), as well as other organs thatmay be at risk of radiation exposure during treatment.

One purpose of the 3D model is the preparation of a radiation treatmentplan. To develop a patient-specific radiation treatment plan,information is extracted from the 3D model to determine parameters suchas organ shape, organ volume, tumor shape, tumor location in the organ,and the position or orientation of several other structures of interestas they relate to the affected organ and any tumor. The radiationtreatment plan can specify, for example, how many radiation beams to useand which angle each of the beams will be delivered from.

In embodiments according to the present invention, the images from theimage system 402 are input to a planning system 404. In embodiments, theplanning system 404 includes a computing system having a processor,memory, an input device (e.g., a keyboard), and a display. The system100 of FIG. 1 is an example of a platform for the planning system 404.

Continuing with reference to FIG. 4 , the planning system 404 executessoftware that is capable of producing printing plans for animmobilization device or devices customized to the patient 304 and tothe treatment plan devised for the patient. The software may itselftranslate the output of the image system 402 (e.g., the 3D model) intofiles that can be used by the 3D printer 406. Alternatively, softwaremay be used by a designer to produce such files based on the output ofthe image system 402 and also based on the treatment plan. The printingplans may be a design for an immobilization device, or it may be adesign for a mold that can be used to fabricate the immobilizationdevice. The planning system 404 outputs the files to the 3D printer 406,which produces the immobilization device(s) and/or mold(s).

The immobilization device 320 can be produced by the 3D printer 406using a range of different materials suitable for such a device; thatis, using materials that have the necessary radiological properties. Ifthe 3D printer 406 is not capable of using such materials, then it caninstead produce a mold that can be used to produce an immobilizationdevice made of suitable materials. The immobilization device 320 can be3D-printed as a single piece, or it can be 3D-printed as multiple piecesthat are subsequently assembled.

The immobilization device 320 so produced can be inspected and tested aspart of a quality assurance plan before the device is used with apatient. If the immobilization device 320 is deficient in some aspect,the printing plans can be adjusted to correct the deficiency before theimmobilization device is used.

Some or all of the process 400 can be implemented on-site (e.g., at thetreatment center). Accordingly, patient-specific devices can be readily,quickly, inexpensively, and effectively produced on-site without anexternal manufacturer, avoiding shipping from and perhaps back to themanufacturer. The number of patient visits can be reduced because, forexample, the immobilization device can be fabricated when the patientarrives for a treatment and/or because the immobilization device can bequickly modified on-site after testing for fit and/or function or whilethe radiation therapy is being performed. Furthermore, theimmobilization devices can be recycled and do not need to be stored.

FIG. 5A illustrates an immobilization device 502 that can be 3D-printedin embodiments according to the present invention. The immobilizationdevice 502 is an example of the immobilization device 320 of FIG. 3 .The immobilization device 502 includes a range compensator 504 and apositioning component 506. The immobilization device 502 in general, andthe range compensator 504 and positioning component 506 in particular,can be made of any suitable material or combination of materialsincluding metal or plastic.

As discussed above, the immobilization device 502 is a patient-specificdevice designed or configured to hold a patient in place. Theimmobilization device 502 can also be designed or configured tocompensate for differences in the amount of tissue that different beamsmay travel through, to provide a uniform dose across a target in thepatient. In addition, in embodiments, the immobilization device 502(specifically, the range compensator 504) is designed or configured toshape the distribution of the dose delivered to a patient. Inembodiments, the treatment beam is a proton beam or an ion beam and therange compensator 504 is configured to locate the Bragg peak of the beaminside the target in the patient. In one such embodiment, the rangecompensator 504 is configured to locate the Bragg peak at the distalportion or edge of the target.

The shape of the range compensator 504 can be designed so that the Braggpeak of a proton beam or an ion beam can be moved within the target bydirecting the beam through different parts of the range compensator. Forexample, as shown in the example of FIG. 5A, the range compensator 504has a non-uniform surface facing the incoming beam. Thus, the thicknessof the range compensator 504 (where thickness is measured in thedirection of the beam path) is not uniform. Consequently, by aiming thebeam at one part of the range compensator 504, then another, and so on,the location of the Bragg peak in the target can be moved along the beampath between the distal and proximal portions of the target to create anSOBP. That is, different thicknesses of material can be placed in thepath of the beam by aiming the beam at different parts of the rangecompensator 504, thus affecting the energies of the particles in thebeam, thereby affecting the distance the particles penetrate into thetarget and the moving the location of the Bragg peak in the target tocreate an SOBP. An SOBP can also be achieved by varying the energy ofthe incident beam using the accelerator and beam transport system 204(FIG. 2 ).

Continuing with reference to FIG. 5A, the positioning component 506holds the immobilization device 502 in place relative to the patient.That is, the positioning component 506 holds the immobilization device502 on the patient in a manner such that, if the patient moves, then theimmobilization device also moves so that it is in the same location onthe patient.

In embodiments, the positioning component 506 fastens the immobilizationdevice 502 to the patient. For example, as shown in FIG. 5B, thepositioning component 506 may consist of or include straps that can beextended around the patient (not shown) to hold the immobilizationdevice 502 (specifically, the range compensator 504) in place againstthe patient. The surface of the immobilization device 502 that faces thepatient can be contoured to match the contours of the patient's body.

In another embodiment, with reference to FIG. 5C, the positioningcomponent 506 attaches to an item 508 worn by the patient (not shown).For example, the patient may wear a garment that includes fasteners(e.g., snaps or VELCRO®) that mate with corresponding fasteners of thepositioning component 506 to hold the immobilization device 502(specifically, the range compensator 504) in place.

In embodiments, with reference to FIG. 5D, the range compensator 504 andthe positioning component 506 are fabricated as a single piece.

FIG. 6 is a flowchart 600 of an example of computer-implementedoperations for producing an immobilization device for limiting movementof a patient on a patient support device during radiation therapy inembodiments according to the present invention. The flowchart 600 can beimplemented as computer-executable instructions residing on some form ofcomputer-readable storage medium (e.g., using the computing system 100of FIG. 1 ).

In block 602 of FIG. 6 , a printing plan for an immobilization device isaccessed from a memory of the computing system. The immobilizationdevice includes features such as those described above in conjunctionwith FIGS. 3 and 5A-5D. Additional information is provided withreference to FIG. 4 .

In block 604 of FIG. 6 , a 3D printer is controlled using the printingplan to fabricate the immobilization device. Additional information isprovided with reference to FIG. 4 .

FIG. 7 is a flowchart 700 of an example of computer-implementedoperations for performing radiation treatment in embodiments accordingto the present invention. The flowchart 700 can be implemented ascomputer-executable instructions residing on some form ofcomputer-readable storage medium (e.g., using the computing system 100of FIG. 1 ).

In block 702 of FIG. 7 , a radiation treatment plan is accessed from amemory of the computing system. The radiation treatment plan prescribesthe dose or dose distribution to be delivered to a target in a patientby an incident beam emitted from a nozzle of a radiation treatmentsystem.

In embodiments according to the invention, dose threshold curves areused to specify limits for the radiation treatment plan. A dosethreshold curve provides a normal (healthy) tissue sparing-dose as afunction of dose rate or irradiation time. The dose threshold curves canbe tissue-dependent. For instance, the dose threshold curve for thelungs may be different from that for the brain. The appropriate dosethreshold curve(s) can be to establish dose limits for radiationtreatment planning. For example, the appropriate (e.g.,tissue-dependent) dose threshold curve can be used to determine beamdirections (gantry angles).

Dose limits can include, but are not limited to: a limit on irradiationtime for each sub-volume (voxel) in the target (e.g., for each voxel oftarget tissue, treatment time less than x1 seconds); a limit onirradiation time for each sub-volume (voxel) outside the target (e.g.,for each voxel of normal tissue, treatment time less than x2 seconds; x1and x2 may be the same or different); a limit on dose rate for eachsub-volume (voxel) in the target (e.g., for each voxel of target tissue,dose rate greater than y1 Gy/sec); and a limit on dose rate for eachsub-volume (voxel) outside the target (e.g., f or each voxel of normaltissue, dose rate greater than y2 Gy/sec; y1 and y2 may be the same ordifferent). In general, the limits are intended to minimize the amountof time that normal tissue is irradiated.

In block 704, the nozzle is controlled according to the treatment planto aim the beam at an immobilization device like that of FIGS. 3 and5A-5D.

In summary, embodiments according to the invention provide an improvedimmobilization device that is multi-functional. In addition toimmobilizing a patient, the device can be used to shape the dosedistribution within a target in the patient. In embodiments, theimmobilization device includes a range compensator. In effect, inembodiments, the range compensator is moved from the nozzle of aradiation treatment system to the immobilization device. Themulti-functional aspect of the immobilization device can improveradiation treatments and reduce costs. The immobilization device can be3D-printed, which provides a number of benefits as well as explainedabove.

Range Compensators Positioned on a Patient for Radiation Therapy

FIG. 8A is a system 800 for treating a patient 804 during radiationtherapy in embodiments according to the present invention. The system800 includes one or more range compensators (exemplified by the rangecompensator 802) and one or more positioning components (exemplified bythe positioning component 806). In practice, each range compensator islocated on the patient 804. The positioning component 806 holds therange compensator 802 in place relative to the patient 804 such that therange compensator lies on a path of a beam emitted from a nozzle of aradiation treatment system during radiation therapy.

Each of the range compensators shapes a distribution of a dose deliveredto the patient 804 by the beam. The dose distribution may be relativelyuniform across the target, or it may be non-uniform (e.g., thedistribution may include a Bragg peak). Each range compensator canproduce a different dose distribution in the target. In effect, therange compensator that conventionally is in, for example, the nozzle ofa radiation treatment system is moved to locations on the patient 804.The range compensators described in conjunction with FIGS. 5A, 5B, 5C,and 5D are examples of the range compensator 802. One or more of therange compensators and one or more of the positioning components can beparts of an immobilization device as previously described herein. Therange compensators and positioning components can be 3D-printed aspreviously described herein.

In embodiments, all of the range compensators are held in place on thepatient 804 with a single positioning component. For example, thepositioning component may be a belt worn by the patient 804, and each ofthe range compensators could be fastened to the belt. In anotherembodiment, the range compensators are held in place individually by arespective positioning component as described in conjunction with FIGS.5A, 5B, 5C, and 5D.

In operation, the nozzle is aimed at a first one of the rangecompensators and the beam is turned on, delivering a distributed dose tothe target along the beam path. That is, the path of the beam passesthrough the first range compensator, which affects the beam to produce aparticular dose distribution in the target according to the design ofthe first range compensator. The first range compensator may have anon-uniform surface facing the beam as described above. In that case,the beam can be scanned across the surface of the range compensator tochange the shape of the dose distribution within the target. The nozzlecan be aimed at the first range compensator by moving the nozzle or bymoving the patient 804 or by doing both (the patient is moved by movingthe patient support device 208 of FIG. 2 ). After the beam is turned onfor the time period specified by the radiation treatment plan (see, forexample, the discussion of FIG. 7 ), the beam is turned off. The nozzleis then aimed at a second one of the range compensators (by moving thepatient or the nozzle or both) and the beam is turned on again. Thus,the path of the beam now passes through the second range compensator,which affects the beam to produce a particular dose distribution in thetarget according to the design of the second range compensator. Like thefirst range compensator, the second range compensator can have anon-uniform surface facing the incoming beam and the beam can be scannedacross the surface of the second range compensator. The energy orintensity of the beam transmitted through the second range compensatorcan be different from that transmitted through the first rangecompensator. The beam is turned off again after the time periodspecified by the radiation treatment plan. This process can be repeatedfor each of the range compensators. In this manner, different beamgeometries are readily accommodated.

FIG. 8B is a perspective view of an example of a beam geometry inembodiments according to the invention. In the example of FIG. 8B, thebeams (exemplified by beam 812) are in the same plane. The beamsoriginate from a nozzle (not shown). Each beam can deliver a relativelyhigh dose in a relatively short period of time. For example, each beamcan deliver at least 4 Gy in less than one second, and may deliver asmuch as 20 Gy or 50 Gy or more in less than one second. In this example,the beams' paths overlap only within the target 814, and do not overlapoutside the target in the surrounding tissue; however, the presentinvention is not so limited.

FIG. 8B shows the range compensator 802 in the path of the beam 812. Theshape of the beam 812 and the shape of the range compensator 802 shownin the figure are for illustration purposes only. In general, the rangecompensator 802 is located on the outside of the patient (referred to asthe patient outline), either on the patient's skin or on an article ofclothing or the like worn by the patient. The beam 812 is aimed so thatit passes through the range compensator 802. The other beams shown inthe figure can pass through other range compensators (not shown).

Although all beams are shown in FIG. 8B, this does not mean that allbeams are necessarily delivered at the same time or in overlapping timeperiods, although they can be. The number of beams delivered at any onetime depends on the number of gantries or nozzles in the radiationtreatment system and on the treatment plan.

FIG. 8C illustrates a perspective view of an example of a beam geometryin embodiments according to the invention. In the example of FIG. 8C,the beams (exemplified by beam 822) are in different planes. In thisexample, the beams' paths overlap only within the target 824, and do notoverlap outside the target in the surrounding tissue; however, thepresent invention is not so limited. Although all beams are shown in thefigure, all beams are not necessarily delivered at the same time or inoverlapping time periods as mentioned above.

FIG. 8C shows the range compensator 802 in the path of the beam 822. Theshape of the beam 822 and the shape of the range compensator 802 shownin the figure are for illustration purposes only. In general, the rangecompensator 802 is located on the outside of the patient (the patientoutline) as described above. The beam 822 is aimed so that it passesthrough the range compensator 802. The other beams shown in the figurecan pass through other range compensators (not shown).

Thus, in embodiments according to the invention, range compensators areplaced at locations on the patient 804 such that each of the beams shownin FIGS. 8B and 8C passes through a respective range compensator. Ingeneral, the surface of a patient can be viewed as having a number ofdiscrete facets through which a beam may pass. From this perspective,for beams other than photon beams, each incident beam is orthogonal to afacet. In embodiments according to the invention, a range compensatorcan be located on each facet.

FIG. 9 is a flowchart 900 of an example of computer-implementedoperations for radiation treatment planning in embodiments according tothe present invention. The flowchart 900 can be implemented ascomputer-executable instructions residing on some form ofcomputer-readable storage medium (e.g., using the computing system 100of FIG. 1 ).

In block 902 of FIG. 9 , parameters for a radiation treatment plan areaccessed from memory of the computing system. The parameters include,for example, the number of beams and paths of the beams relative to aposition of a patient on a patient support device.

In block 904, locations on the patient for range compensators areidentified. Each range compensator is strategically located on thepatient so that each range compensator lies on at least one of the beampaths. Each range compensator shapes a distribution of a dose to bedelivered to the patient by at least one of the beams.

FIG. 10 is a flowchart 1000 of an example of computer-implementedoperations for radiation treatment in embodiments according to thepresent invention. The flowchart 1000 can be implemented ascomputer-executable instructions residing on some form ofcomputer-readable storage medium (e.g., using the computing system 100of FIG. 1 to implement the control system 210 of FIG. 2 ).

In block 1002 of FIG. 10 , a radiation treatment plan is accessed frommemory of the computing system. The radiation treatment plan prescribesa distribution of a dose to be delivered to a target in a patient by anumber of beams emitted from a nozzle of a radiation treatment system.

In block 1004, the nozzle is controlled to aim the beams at rangecompensators positioned at different locations on the patient. Eachrange compensator shapes a distribution of a dose delivered to thepatient by a respective beam. The nozzle is aimed at a first rangecompensator, and then a first beam is turned on and emitted at the firstrange compensator. The first beam is then turned off, the nozzle isaimed at a second range compensator, and a second beam is turned on andemitted at the second range compensator. This process can be repeatedfor each of the number of beams.

In summary, range compensators in embodiments according to the inventioncan be used to shape dose distribution in the target in lieu of, butalso in combination with, a conventional range compensator. Bystrategically locating the range compensators on the patient, differentbeam geometries are readily accommodated. For radiation therapyincluding FLASH RT, it is not necessary to wait until a rangecompensator is adjusted when the beam geometry changes; instead, aproperly configured range compensator is already in place. Thus,radiation therapy including FLASH RT can be quickly performed, therebyfacilitating patient comfort. Range compensators in embodimentsaccording to the invention also can be used to provide the prescribeddose inside the target and thus can facilitate radiation treatmentplanning using FLASH RT by making it easier to address that aspect ofthe planning.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A system for treating a patient during radiationtherapy, the system comprising: multiple range compensators; and asingle positioning component coupled to the multiple range compensators,wherein each range compensator of the multiple range compensatorsrespectively shapes a distribution of a dose delivered to the patient bya respective beam of a plurality of beams emitted from a nozzle of aradiation treatment system along different paths between the nozzle anda target in the patient, and wherein the multiple range compensators arelocated on the single positioning component to hold the multiple rangecompensators in place on the patient at respective locationscorresponding to the different paths.
 2. The system of claim 1, whereinsaid each range compensator has a non-uniform thickness measured in thedirection of the respective path of the respective beam.
 3. The systemof claim 1, wherein the plurality of beams comprises beams selected fromthe group consisting of proton beams and ion beams, and wherein saideach range compensator is configured to locate a Bragg peak of therespective beam inside the target in the patient.
 4. The system of claim1, wherein the multiple range compensators are part of an immobilizationdevice that limits movement of the patient on a patient support devicerelative to the beams.
 5. The system of claim 4, wherein the singlepositioning component fastens the immobilization device to the patient.6. The system of claim 4, wherein the single positioning componentfastens the immobilization device to an item worn by the patient.
 7. Thesystem of claim 1, wherein the single positioning component has a shapethat fits contours of the patient.
 8. The system of claim 1, wherein themultiple range compensators and the single positioning component arefabricated as a single piece.
 9. The system of claim 1, wherein theradiation treatment system is coupled to a treatment planning systemcomprising a computing system having a processor and memory, wherein thetreatment planning system is coupled to a three-dimensional printer. 10.The system of claim 9, wherein the treatment planning system furthercomprises an image system operable for imaging the patient.
 11. Thesystem of claim 1, wherein each beam of the plurality of beams deliversa dose rate of at least four grays in less than one second.